The Clinical Core (CC) maintains our Longitudinal Cohort (LC), an ethnically and demographically diverse cohort which is the central scientific resource of the UCD ADC. The CC supports the research mission of the ADC to assess how various risk and protective conditions differentially affect cognitive trajectories across the spectrum of cognitive ability. The Core has achieved target enrollment in the LC (n ~530) and now has 2 or more visits on 88% of participants;approximately one-half of LC participants are of minority ethnicity, generally African American or Hispanic. In order to facilitate study of early AD and clinical transitions, about 50% of the LC is cognitively normal, 20% MCI. and 30% demented (59% of whom were non-demented at entry). The CC recruits participants primarily through direct, outreach based community recruitment, and also through ADC clinics. Recruitment now focuses on replenishing the cohort and meeting particular needs of associated scientific projects. It works closely with the Education and Information Transfer Core on recruitment and retention of the LC. The CC consents, evaluates participants in the LC. obtains autopsy preconsents and annual follow-up. The Core provides reliable and valid diagnoses for each participant. It implements standardized clinical data collection protocols, obtaining clinical data including all elements of the UDS. In concert with the Neuropathology Core, it arranges collection of biospecimens (e.g. plasma. DNA. RNA) and works closely with the Neuroimaging Core to obtain research MRI and other brain imaging studies. In addition, it coordinates, enables and monitors the collection of additional data that are crucial to a variety of thematically connected, independent research projects supported by the ADC. Because the Core is so tightly, and synergistically. integrated with independent projects, all participants in the LC also participate in a variety of R01s. The Core implements numerous procedures to maintain data quality and reliability, including monthly clinicopathological case conference (conducted with the Neuropathology Core). The Core supports recruitment for studies by ADC investigators, including pilot studies. The Core maintains a Clinical Trials Unit that carries out industry and academically sponsored diagnostic and treatment trials.